1. Field of the Invention
The invention relates to apparatus for removal of snow, slush, or ice from highways, airport runways, or other travel surfaces such as driveways, sidewalks and the like (hereinafter referred to as "travel surfaces"). The invention is particularly useful for the removal of snow and ice from travel surfaces which have irregularities in contour; e.g. depressions, potholes, etc.
2. Description of the Prior Art
In removing snow from travel surfaces, it is common to use a snowplow blade, which is attached to the front of a vehicle that is capable of moving in the snow, such as a truck, a tractor or an all-wheel drive vehicle.
It is recognized that snow blowers have been used in the past but their use has been limited to narrow travel surfaces, such as walkways, driveways, etc.
When using snowplow vehicles, the downward travel of the snowplow blade is usually limited, such as by means of skids so as to prevent the bottom edge of the snowplow blade from scraping the travel surface and damaging the same. Even when not limited by skids, the snowplow blade is preferably moved along just above the surface to be cleaned so as to avoid excessive scraping upon that surface and damage thereto. However, because many parts of a travel surface are not flat, there are significant variations in the distance between the lower edge of the snowplow blade and different parts of the travel surface, making snow removal uneven over different parts of the travel surface. This can result in leaving a layer of snow beneath some segments of the lower edge of the snowplow, which snow is compressed by the weight of the snowplow and subsequent passing vehicles, making the travel surface slippery and unsafe. This may necessitate the use of salt, sand, etc. which is expensive to lay down on large travel surfaces. Furthermore, even when the snowplow blade is adjusted so as to be as close as possible to the surface to be cleaned, because of the "crown" which is on some travel surfaces, and because of minute depressions and irregularities therein, there are substantial patches of snow and ice remaining after conventional snow removal.
Various attempts have been made to solve the above-mentioned problem, or similar problems. For instance, in Bunnell U.S. Pat. No. 520,479 (May 29, 1894) for a Road Scraper, the inventor proposed having a segmented lower edge for a road scraper blade, with the edge segments being attached to the main blade by a continuous rubber strip. That arrangement is not presented as a dual blade snowplow, but rather as a scraper for dirt roads which, in theory, will conform to the crown of the road. In that structure, since the individual segments of the blade edge are fairly wide, and since the segments are not completely independent in movement, but are mounted to a common rubber mounting strip, the above-mentioned objective is not completely realized.
U.S. Pat. No. 2,936,537 issued May 17, 1960 to E. C. Bain for a Snow Plow, is directed specifically to a follow-up cleaning of snow left by the snowplow blade. However, that device works by the application of jets of compressed air to the snow missed by the plow, together with a rubber flap to confine the air within a channel behind the plow blade. That system can be effective for loose snow, but is not believed effective for packed snow, or ice or heavy slush. Also, the provision of the air jets presents problems, including the expense of installing and maintaining the compressed air equipment, and the vulnerability of the air jets to clogging.
U.S. Pat. No. 2,962,821, which issued on Dec. 6, 1960, discloses a snowplow having a plow frame and guide pocket members.
U.S. Pat. No. 3,199,234, which issued on Aug. 10, 1965, discloses a snowplow having an obstacle compensating means on the forward edge of the blade. In FIG. 2 it is shown how the snowplow compensates to accommodate an obstacle located on a travel surface.
U.S. Pat. No. 3,808,714, which issued on May 7, 1974, discloses a double-bladed snowplow having an overload release.
U.S. Pat. No. 2,061,585, which issued on Nov. 24, 1936, discloses a snowplow blade for clearing tracks.
U.S. Pat. No. 1,922,998, which issued on Aug. 15, 1933, discloses a combined pan scraper shovel and broom which obviously has limited utility for large road surfaces.
U.S. Pat. No. 1,432,352 discloses a snowplow that is attached to a locomotive for clearing railroad track.
U.S. Pat. No. 1,383,409, which issued on Jul. 5, 1921, discloses a snowplow which can be affixed to the front of an automobile.
Russian Patent 400669 discloses a snowplow of general interest.
The references discussed, while teaching snowplow blade structure and snow removal, do not teach a simple economical means for effectively removing snow from uneven surfaces.